Proposed studies are directed at the hypothesis that immunologic abnormalities mediate tissue inflammation and injury of chronic rheumatic disease and that the environmental factors involved are microbial in nature. Efforts to demonstrate latent infection in tissue culture lines, derived from patients with rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) utilize techniques for rescue of infectious virus and indirect methods for detection of viral transformation of cells. Efforts to identify the immunologic stimulus involved in these diseases will involve purification and characterization of immune complexes and studies of the immunoreactivity of immunoglobulins produced by tissue-derived lymphoblastoid lines. The role of genetic factors in RA and SLE will be assessed in continuing studies of twins and other selected family groupings.